Glass slide has been conventionally used in the art as a substrate for the fabrication of DNA chips and protein chips. It has been noted, however, that glass slide has several disadvantages as a substrate of biochips. Firstly, glass slide itself is fragile and has to be handled carefully. It is not easy to chemically modify the surface of glass slide in order to successfully immobilize biological, small molecules (such as metabolites from plants or herbs) to said modified surface for binding directly. Glass slide may produce an undesired, high background signal that interferes with the analysis of the biochips that are sequentially treated with a label. There has been a demand in the art to create a new material or develop a material that could be easily modified in replace of glass as a biochip substrate.
Recently, an effort in the development of a plastic slide-based biochip has been made, based on the ground that a plastic slide is not only more effective in cost than a glass slide, but also can be easily molded into a shape as desired by a conventional injection moulding process.
WO 00/55627 disclosed a biochip for the detection of target analytes, comprising an array of biologically binding ligands immobilized to a non-fluorescent acrylic support.
WO 00/36145 disclosed a method for making a biochip, comprising grafting biological probes on a conductive polymer.
EP 1 026 259 disclosed a DNA chip comprising a solid carrier and oligonucleotides or polynucleotides fixed on the solid carrier in the presence of a hydrophilic polymer.
Though a plastic substrate has been used for the fabrication of DNA chips, however up to date it has not been successful in the art to use a plastic slide, with its surface having been chemically modified, for immobilizing proteins, peptides or small molecules to its treated surface, preferably in microarrays, especially at a condition that those proteins, peptides or small molecules have not been modified.
In addition, there was no teaching or suggestion in the art that a plastic slide made of polystyrene could be treated in one step on its surface with a simple reagent, whereby oligonucleotides or polynucleotides could be immobilized, preferably in microarrays, to its treated surface.